Drivetrain Types

The main components of a vehicle's drivetrain that relate to weight distribution and transfer are the position of the engine and the wheels that are powered by it. Many low-end economy cars are front-engine, front-wheel-drive, while sportier rides tend to favor the front-engine, rear-wheel drive setup. There are also mid-engine arrangements and all-wheel-drive vehicles. Each variation affects the handling and acceleration dynamics of vehicles.

The placement of a vehicle's engine directly affects the weight balance of a car. A front-engine vehicle will tend to have a frontal weight bias. While this may help give the front wheels traction during cornering, it may also result in too little weight holding down the rear end of the car. Under extreme speed, this lack of traction in the rear quarters of the car may result in oversteer, as the tail end breaks loose and kicks out ahead of the front wheels. Still, you'll find the vast majority of vehicles have their engines located at the front of the car, from econoboxes like the Chevrolet Cobalt to performance powerhouses like the Corvette Z06.

Conversely, you'll find very few vehicles with a rear-engine arrangement. Pretty much only Porsche is crazy enough to put their engines at the far rear end of their 911 (some Volkswagens do it, too). The added weight to the rear may help keep the rear tires planted during acceleration, but may also contribute to oversteer if the weight is pushed too far in a corner. As well, having the weight of the engine at the back of the car tends to eliminate understeer. More commonly though, you'll find vehicles with a mid-engine arrangement. Though the engine is still located aft of the driver, it's positioned more toward the center of the vehicle, in front of the rear axle. This mid-engine arrangement gives a vehicle the benefit of improved weight balance. Vehicles like the Lotus Elise and Ferrari F430 have this mid-engine arrangement.

A front-wheel-drive (FWD) car has engine power delivered to the front wheels. The benefit of this setup is easy, simple control that's difficult to lose. Front-wheel-drive vehicles are great cars to start with because they're typically not as rowdy as other drivetrain setups. A mistake in a FWD vehicle will generally result in manageable understeer, rather than out-of-control oversteer. The downside is that the FWD setup is inherently detrimental to acceleration.

As we discussed earlier, as a vehicle accelerates its weight balance transfers to the rear wheels. As the weight shifts away from the front wheels, those front wheels lose traction. Since the acceleration of a front-wheel-drive car is dependent on the traction of the front wheels, this weight transfer limits acceleration. Also, high-powered FWD vehicles tend to suffer from torque steer. As the front tires share the responsibilities of both acceleration and steering, there's a real chance that quick acceleration off the line can tug the steering left or right. As such, you'll find that few performance-minded cars have FWD drivetrains.

In the real world, front-wheel-drive has many practical benefits, including cheaper manufacturing costs, less weight and less drivetrain power loss resulting in better fuel economy, in addition to generally taking up less space, leaving more space for passenger and cargo room. Still, we would never ever pay more than $25,000 for a FWD vehicle because all the practical benefits of FWD are much less cool than the performance benefits of RWD and AWD.

The vast majority of performance vehicles are rear-wheel-drive (RWD). The inherent strength of RWD is clear when you understand weight transfer. As we explained, under acceleration the weight balance of a car shifts backward, pushing down on the rear wheels. This added weight means added traction, a must for quick acceleration both off the line and out of corners.

The downside to rear-wheel-drive is that it tends to be more difficult to control than other drivetrains. Hop into a powerful RWD vehicle like the Corvette Z06 and you'll quickly become familiar with the monster known as oversteer. During cornering, application of the throttle will tend to break traction to the rear wheels and send the rear end of the vehicle scooting out ahead of the front wheels. In road racing, this is never a good thing. Not only does the loss of traction to the rear wheels result in reduced speed, but it's also potentially dangerous. Unchecked oversteer can quickly send your car into a spin and off the track.

Despite the learning curve for RWD vehicles, this drivetrain setup is generally regarded as the best for road racing application. Skilled drivers can work with the driving characteristics of rear-drive vehicles for an optimal balance of control and speed.

In all-wheel-drive (AWD) vehicles, engine power is delivered to all wheels of the car, though usually not all at once. AWD vehicles have a sort of inherent, if not simple, traction control system. Most typical, low-end AWD vehicles will favor power delivery to the front wheels. However, if the car senses that the powered wheels lose traction, the car's computer automatically transfers the power away from the low-traction tires to other tires that do have plenty of traction.

The benefit of AWD is especially apparent during hard acceleration off the line. As the car's computer shifts power to the wheels with the most grip, AWD vehicles really hook up with the asphalt and go. All-wheel-drive strengths are even more pronounced in compromised driving conditions, like driving on a wet track or driving in dirt. The benefits are also helpful in corners where power-on oversteer is minimized by the car's computer wizardry.

Because of the smart characteristics of an AWD drivetrain, all-wheel-drive vehicles have many of the performance benefits of a RWD setup while maintaining the easy controlability of FWD setups. However, there are some compromises. Like FWD vehicles, AWD cars tend to suffer understeer more than their RWD rivals. As well, all-wheel-drive drivetrains add weight and mechanical complexity to cars, neither of which are desirable in real-life road racing. Still, AWD vehicles present a solid balance between rear- and front-wheel-drive vehicles and should definitely be considered by neophyte racers.